View Full Version : Stock spark plug wires, 7 or 8 mm?

10-03-07, 08:50 AM
I just replaced my spark plug wires with Bosch Premium 09734 wires. They are 7mm wires. The wires that I took off were 7mm also. I think they were the stock wires. I still have a slight miss so I checked for any arching at night in the dark. I noticed that the wires were arching to the fuel injection harness in a couple places and to the intake manifold cover post in another place. I moved these wires around to avoid being close to any ground and the motor seems to run better.

When I bought the wires I was hoping they would be 8mm wires. Bosch uses 8mm wires in other applications. I guess they just matched the diameter of the stock wires. With the high voltage required to fire two plugs at a time, I think they should be using 8mm wires. I'm going to wrap most of the wires with that flexible wire conduit and see if that helps. Has anyone else had this problem?

10-03-07, 10:10 AM
I put 7mm on my 96 and never had a problem. I would change your plugs and resize the wires if they are too long and crossing each other.

10-03-07, 04:22 PM
If, for some reason, the insulation on the wire is insufficient, you will have corona and arcing: 7mm, 8mm, 11mm.....it doesn't matter. IF the insulation is no good, extra wrap is a BandAid. Make your own from a Taylor, Accel, or Moroso 8mm kit. Go online and look at PerformanceAutomotiveWarehouse (PAW) in Chatsworth, CA. The LAST thing you want is wires, particularly long wires, running closely parallel to each other. Crossing at near 90 deg. is far preferable.

10-03-07, 05:06 PM
You are not the first to say that they had problems with Bosch. I'd stick with A/C Delco.